Alloy



Je 2l, E928- 3,674,958

R. S. DEAN ET AL ALLOY Filed June 21, 1924 Jil?? n armas naar aantast n, il .ML s

REGINALD SCOTT DEAN D WILLIAM EWART HUDSON, OF OAK PARK, ILLINOIS, AB-

SIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, F NEW YORK, N. Y.,

i A CORPORATION 0F NEW-YOBK.

Application led''une 21,

This invention relates to improved alloys. By improvementVinl allo sis meant increase in hardness and the ike which is secured by -the treatment- -known as f agehardening.

' Heretoore, alloys having three or more constituents, such as duralumiii, a composition of aluminum, silicon, copper and magnesium have been improved by age-harden-` ing. Such a process, however, has not'been successfully applied to binary alloys. Nor has means been provided for obtaining improvement in a articular metallic alloy. eX- cept the old met od of continued trial, commonly called the cut and try method.

l The object of this invention is to provide improved bina alloys.

he process means ofwhich the improved binary, a loys embodying the invention may be produced, consists in adding to ,a meta another metal or pseudo metal d which will form a solid solution with the Vfirst-mentioned metal, the two constituents being' of such a nature that the solute is more solublel at one temperature than another, forming a solid solution of the resulting alloy by heating and then quenching andJ aging ment is obtained by employing the greatest 3o amount of solute which is soluble in the solvent metal at any temperature at which the resulting alloy is a solid, other steps of the process, including heating, quenchingl and aging, beingY controlled in a manner a5 which will be explained more in detail hereinafter.- Y

Other features and objects of the invention willl ap ear from a consideration of the ollowin l t@ larly pointed out in the appended ln the attached drawing,

Fig. 'l is a .graphic curve showing the relationship .ofsolubility of antimony in lead jat-'various' temperatures, .to the improvement 'obtainable in lead alloyed with var ibus percentages of antimony; and

aims.

Fig. 2 is a similar curvelotted on these characteristics-of-lead-tin a oys. j

This invention is based rimarily on the ao discover that -metallicA a oys can .be imv proved y age-hardenin when they are of, such a nature that one o the constituentsl is thealloy. A marked improve-pl escription, and .will 4be 1particu-l riiary ALLOY.

i924?. serial no. 721,432.

soluble in the other while in the solid state and when the solubility changes with change in temperature, and that a marked improveture sufliciently high to form a solid solution thereof, the alloy then being quenched to form a supersaturated solution and finally allowed to age until the alloy has assumed a substantially stable state.

A detailed description will nowvbe given 'of the mechanicsof the process and the mariner in which it may be performed. lt has been found in practicing the process that the nfollowing variables are present which have van effect upon the improvement attainable in any particular alloy.

. Composition of the alloy.

.- Temperature of heating.

Time of heating.

. Size of the mass heated.

Shape of the mass heated.

Temperature from which quenched.

Temperature of quenching bath. Temperature during aging.

. Time of age treatment.

)Each of these variables will now be taken up individually and be discussed in relationship to the other variables. A

l. Uompositz'on of theaZZoyf-lt is oft/en @aannemer-@we .found in considering any particular binary alloy which is of such a nature that one of the materials is soluble in the other, that greater solubility is obtained at one temerature than at other temperatures. For instance, asv ointed out in our copending application erial No. 690,716, tiled Feb- 5, 19524, antimony is more soluble in lead at the eutectic fusing temperature than at any other point. Any alloy which shows av greater solubility of its-solute constituent at ighertemperatiires .than at lower tempera- .tures andwhile the alloy is in the solid state, may be4 age-hardened, and a marked iin- -provement is obtained by employing the maximum amount of solute constituent which is soluble inthe solvent metal while the'alloy' isvvin the solid state, or, as stated solution with the' solvent metal.

= A Study in another way,'by employing the maximum amount of solute which will enter into solid of the 'curves shown in the at- Y. tached drawing will'show more clearly the relationship of solubilityl to hardness.

Fi 1 is a composite graph showing a tensi e strength curve 'superimposed over a curve which 1s shown as a dotted solubilit y line. y' T e figures on the right of the graph show vAthe,-jcentigrade temperature yat which varyingpercentages of antimony, calibrated on -tlleglower 'linel are soluble in lead. The

1 solid-.line represents increase lin tensile strengthby age-hardening. The gures on n the left hand-margin representimprovement indicated in terms of tensile strength, and

the relationship of. the improvement to the of the two curves the maximum improve- 4 Aslightly over 7,000 lbs. per square inch and l this improvement lis obtainedby employing 3o antimony content may be seen by comparing the dotted solubility curve and the sohd tensile strength curve. v As IisA indicated by the position and shape ment in tensile strength indicated at A is about 2.45% antimony with pure lead in the compounding of the alloy. The dotted line i indicates that atv between 245 C. and 250 C. the maximum solubility vof antimony Ain v lead while in the solidstate is 2.45%, corresponding precisely with theA amount which,

other steps of the age-hardening process be-- married out, causes a marked The temperatures at which various percentages of tin are soluble are read' from the right hand margin,while the Brinell hard' 'n ness is indicated'on the left hand margin.

Point B indicates the maximum improvement obtained and is analogous to the point `A in Fig. 1. lt will be observed that if the tin4 content is read on the lower Vline 'fromthe point B, the ligure 14.5 is obtained and this. as the dotted line indicates, is a proximately the limit of solid solubility o tin 'in lead at any temperature at which the alloy is a solid. These figures show that ,the per- 'centage of maximum solubility and the per'- `centage of maximum improvement coincide,

that the maximum amount of tin soluble in solid lead is about 14.5% and that the. eat- `est-'improvement by a-hardg A1s ob-v tained by emplo 'ng i. ut 14.59 tin and 85.5% remi. y1 Q The hardness ot this material was de- Levante mined by means of a micro-Brinell machine usinga one-sixteenth inch ball, and a two kilogram weight.

2. Temperature of maximum-improvement the temperature em-A ployed during the heating of the alloy must be a temperature at which all of the solute material employed will enter solution.- For with 2.45% antimony, {which isl about lthe maximum amount of antimonywhich will enter solid solution, ,the alloy must be heated n at a temperature slightly below' the eutectic fusing temperature. lf a percentage 'of soluteis employed which will enter solution atanother temperature than that of maximum solubility, another temperature may be employed to obtain the improvement heating-#To obtain Linstance, if 97.55 parts of lead are alloyed i .ble with the amount of solute constltuent f ever, that if the-J` maximum percentage of solute is not employed', no hanm'wlll come from heating the material at the temperature l atwhieh the maximum solubilit occurs. In

vcarrying" out anl age-hardenlngmethod,

therefore, it `is advisable and desirablel to employy as near `as possible in the heating step the rtemperature atv which maximum l solubility occurs. For most metallic alloys this will mean heating at a temperature Fslightly below the eutectic fusing temperature. ,3.1 Time of"`heatng. -To `obtain desirable :results the heating is preferably carried on for a sutlicient length df time to obtain a per'- feet homogenePous solid solution. Although the percentage of material that .will enter lUt into solutibn ma be said-to be a certain amount, where .differentialV -solubility is observed at various temperatures, it invariably takes vsome time to .obtain a-hoinogeneous solid solution with that amount of solute at the temperature employed. lIor instance, as shown in our copending ap hcaton referred to above,the percentage o antimony whicha 11( is soluble in lead at "240 C. is about 2.45%. A

Supposing, the temperature is' in accorda-nce with there uirements stated intthe previous tion with this percentage ot antimony it is necessar to heat vthe alloy sometimes as long -as l2 hours before homogeneity is obtained.

paragraph, morder to obtain a perfect solu- This is kan important step in the-treatment of age-hardened alloys because if a perfect honlogeneous solid solution is not obtained the improvement of the metal may be very adverselyalienated.A .4

4. Size shape of the A'maar' heated-.4- lf xone ofthe constituents `be appreciably lighter -in 'weight-,thanthe balance of the alloy, it has a tendency to rise to the top when the molten 'alloyis cast into sa mold. -s an exampla-,aatimony is considerably lighter thanlead 'and ithas been observed that it will rise to the top of a mold, paris obtaining solid solution. Segregation simply lengthens the time required for "solid solution to form at the temperature emploved.

6. Temperature from which quenched.- In order to obtain the best results the. material should be quenched while in a state of solid solution. This means `that quenching must take place at about the temperature which is necessary to obtain solid solution, that is, the temperature of thc heating step. However, if the material enters into solution quite slowly, it will usually be found to stay in solution and separate out quite slowly. When this is the case quenchingr may take place at a slightly lower or higher -temperature than the temperature at which the first heatilig is carried on.

7. emperature of .the quenching bath.- The purpose of quenching is to quickly change the temperature of the material to bring it to its normal temperature without permitting a change in the lattice or structure of the material itself, that is to say, the material is retained in substantially thel same condition as it was in at the higher temperature. Quen^hing, therefore, may be accomplished in any manner which will have .this

result. For many alloys, for example leadantimony, quenching can be etected by means of water at room temperature. v

8. Temperaturedum'ng,agingsfAging may take place at any temperature which will allow suiiicient molecular mpvement in the v material to accomplish the age-hardening. Y In general, aging can be accomplished more quickly at a higher `temperature thanl'at a lower temperature. It is also generally` the case ythat aging should n'ot take place` at a` high enough temperature to permit annealing of the alloy which git is sought to age.l The critical temperature is usually termed the temperature of recrystallization. It has been found ,that in order to secure high" tensile strength and hardness it is advantageous to age the alloys at temperatures at 'which the solute constituent. -precipitates` from the supersaturated solution in a finely ydivided form, or in other words, ata temperature low enough to insure little agglomeratlon of the precipitated-particles. Since centavo of are much smaller in size than the agglomerated particles produced by other methods of ftreating binary alloys.

9. Time of age treatment-The time required for aging a particular alloy will vary with the temperature. Some age-hardened alloys will continue to show an increased hardness or improvement over a long period of time. For instance, lead antimony alloys will `show a' very great hardening after 72 hours aging at room temperature. It is ob# servable, however, that even after a matter of months, they will continue to harden gradually. This after-hardening effect, however, is not great, but it shows the amount of time that must sometimes be allowed before the maximum aging will have-taken place and likewise will be definitely concluded. If, however, the preliminary steps, that is, the composition requirements, time and temperature of heating, temperature from whichquenched and temperature to which quenched, are such as to cause a miximum hardness, the agin will have the effect of causing maximum hardness in time, even if it. is materially `retarded on accountof the em loyment of too low a temperature. v

he subjectmatter of the present invention can be applied not only to binary alloys which show the characteristics described, but also 'to lalloys which may be referred to as pseudo-binary alloys. An example of this type of alloy is lead, copper and antimony, particularly when certain percentages are employed.4 As an-example, a small percop er added to lead-antimony has the eil'ect oi) causing increased solubility of thev antimony in lead. The amount of antimony soluble in lead at the eutectic fusing temperature is about 2.45%. When .1% of copper, howeverys added, this is increased to 3.25%. The same process which is applied t'o the ordinary binary alloys, having` the properties referred,to,can lalsobe applied to such an alloy as lead, copper and antimony. The vprocess constituting the present invention may also be applied to certain binary i constituents 1s not vdirectly soluble in the other. As an example, an alloy wherein two alloys -in which-one of the the carrier material, or whether a chemical compound is formed and the compound then goes into solution in the carrier material.

Where a solid solution is formed and reference made to such solid solution in either,

the description ofthe invention or 'the appended claims, it is intended to include in the ternfs0lid solution'either type of soluening independent of the underlying theory p being the subject-matter of the mvention.

It will-be noted from a study of the hardness and tensile strength curves in the attached figures that there is some latitude over which disirable results are obtained. Each one of the curves is partially flat on top, andthe composition indicated by reading from the center of the fiat portion represents the greatest improvement. It is not desired, however,A to lnnit this invent-ion to a method for obtaining the hardness resulting by employing the percentage of alloying matter shown on a representative curve as the point equivalent tov the point A in Fig. 1. lVe have determined that a variation of about 20% in volume of the solute material will not cause any great departure from the desired improvement. pended claims, therefore, substantially has been employed to ydescribe a departure of about 20% from the maximum amount In the ap- Lavaca@ terial.' l

Although reference has been made throughout to specific applications of .the process, it is to be understood that such reference is not meant to be a restriction, but that the invention is to be limited only by the scope of the appended claims.

What is claimed is: 1'. A lead-antimony alloy in which lead is the major constituent, characterized by the presence of finely divided particles of of solute material soluble in the carrier maantimony substantially uniformly dispersed l throughout the lead.

2. A lead-antimony alloy containing the greatest amount of antimony which will enter solid solution -in .lead at any temperature, and characterized by the presence of finely divided particles of antimony substantially uniformly dispersed throughout the lead.

3. A lead-antimonyalloy containing from lVILLIAM EWART HUDSON. v

l to 2.5% antimony, and charactized by the 

